The present invention relates to tire bead seating tools and is directed more particularly to a collapsible tire bead seating tool that is specially adapted for use in seating the beads of heavy tubeless truck tires.
One of the chief difficulties associated with the changing of tubeless tires is the difficulty of establishing the initial airtight seal between the bead of the tire and the bead-seating surface of the rim on which it is to be mounted. This difficulty results from the fact that, when a tire is uninflated, the opening or gap between its bead and the bead-seating surface of the rim is often so large that seating is prevented by the leakage of inflating air therethrough. The problem is that, at the same time that a large gap renders the tire unable to hold air, the inability of the tire to hold air prevents it from expanding so as to reduce the size of the gap. This problem is most serious in the case of heavy truck tires, particularly radial truck tires, because the stiffness of such tires makes them resistant to forces that tend to reduce the gap sufficiently for seating to occur.
Prior to the present invention a number of different tools have been developed in an attempt to solve the above described problem. One class of such tools, which are best described as pneumatic although they may include some non-pneumatic elements, rely on tubes of elastomeric material that are inflated to compress the periphery of the tire. One example of such a tool is described in U.S. Pat. No. 3,480,067, issued to M. Iglewitz on Nov. 25, 1969.
another class of such tools, which are best described as mechanical although they may include pneumatic or hydraulic actuating elements, rely on flexible belts or chains that are shortened in an attempt to compress the periphery of the tire. Example of tools of this type are described in the following U.S. Pat. Nos. 3,578,059, issued to J. Uhen, et al. on May 11, 1971, 3,710,837, issued to O. Blomgren, et al. on Jan. 16, 1973; and 4,166,493, issued to B. Bosen on Sept.4, 1979. An example of a purely mechanical, ratchet driven seating tool is a model T130 bead expander sold under the trademark "Ken-Tool".
In spite of the variety and ingenuity of the above described types of seating tools, it is not uncommon to encounter tubeless truck tires, particularly radial truck tires, which can be seated only with great difficulty, after numerous attempts, or which cannot be seated at all. One reason for this limited success is the fact that such seating tools do not take into account the effect of the extremely high levels of friction between the flexible belts, etc. and the tread of the tire. One such effect, which is most common in relatively compressible truck tires such as bias ply truck tires, is that the tire is compressed more in the vicinity of the belt shortening mechanisms than it is elsewhere, i.e., is subjected to a compressive force which is distributed non-uniformly or asymmetrically around the outer periphery of the tire. This asymmetrical distribution, in turn, propagates to the interior periphery of the tire where it is manifested as an asymmetry in the tire-rim gap, thereby reducing the probability that the tire will seat easily.
A similar effect, which is most common in relatively incompressible tires such as radial truck tires, is that the tire slips more in relation to the flexible belts in the vicinity of the belt shortening mechanism than it does elsewhere. As in the case of bias ply tires, the result is an asymmetrical distribution of force around the outer periphery of the tire and a corresponding asymmetry in the tire-rim gap, again reducing the probability that the tire will seat easily.
Another reason for the limited success of seating tools used prior to the present invention is the fact that, to the extent that they recognize the negative effect of tool-induced tire asymmetries at all, they tend (1) to attribute such effects to the geometrical asymmetries of the tool that result from the shortening of their belts and (2) to deal with such tool asymmetries by making their belts relatively flexible The idea behind this approach is apparently to rely on the effect of the outward radial forces exerted by the tire to force the belt to remain substantially circular as it is shortened. The problem with this approach is that, while it deals with tire asymmetries that result from non-circular tool geometries, it does not deal with tire asymmetries that result from the concentration of tire compression or slip in the vicinity of the belt shortening mechanism.